1. Field of the Invention
The present invention relates to a galactooligosaccharide composition, preparation, and application thereof. Particularly, the present invention relates to a high-purity galactooligosaccharide composition and preparation thereof, and a method of regulating blood glucose level and improving gut microbiota with the high-purity galactooligosaccharide composition.
2. The Prior Art
Galactooligosaccharides (GOS) are one type of non-digestible oligosaccharides (NDOs). They are oligosaccharides composed of two to ten galactose units and one terminal glucose moiety, and they are classified into galactobiose, galactotriose, galactotetraose, and galactooligosaccharide with five or more sugar units according to the number of monosaccharide units they contain. Commercial GOS products are mixtures of GOS with different molecular weight that have varied compositions. Due to differences in manufacture process, they contain various amounts of lactose, sucrose, glucose, and galactose. GOS products have a fairly wide application in industry, including food additives and pharmaceutical compositions, and their application fields vary depending on the sugar content of the products. For example, under an ideal condition, GOS products suitable for lactose intolerance patients should contain no lactose, and GOS products for reduced calories should lower monosaccharide content.
The well-known methods of GOS preparation are generally divided into enzymatic transformation and fermentation by microorganisms. However, the crude GOS products obtained by these methods contain residual monosaccharides such as glucose and disaccharides such as lactose. To meet the market requirement, studies in related fields have started to focus on improvement of GOS preparation processes to lower the content of monosaccharides and disaccharides. The proposed strategies include utilization of chromatography or membrane filtration methods such as ultrafiltration and nanofiltration for direct removal of monosaccharides and disaccharides from the crude GOS products, or enzymatic oxidation of monosaccharides and disaccharides to form sugar acids which are subsequently removed by ion exchange chromatography, or depletion of monosaccharides and disaccharides by microbial fermentation. Nevertheless, it is inefficient to remove lactose by chromatography or membrane filtration methods; the enzymatic oxidation process is too costly and difficult to scale-up for industrial production; and microbial fermentation requires two or more strains of bacteria or fungi to effectively remove monosaccharides and disaccharides, which complicates the manufacture process.
Accordingly, there is a need to develop a method for industrial production of a high-purity GOS composition with low cost and simplified process in order to provide a GOS composition free of monosaccharides and disaccharides.